Many kinds of removable band-type couplings for pipes exist in the art. It is noted that throughout the specification and claims, the term “pipe” encompasses any kind of generally cylindrical object.
FIGS. 1A-1D illustrate a prior art gasket (seal, the terms being used interchangeably) for a pipe coupling, namely, the HYMAX GRIP 7″ gasket (198-230) LW, from Krausz Industries Ltd., Israel. The gasket has a ring shaped hydraulic seal 1 made of rubber or other resilient material. As seen best in FIG. 1C, seal 1 includes an outer portion 2 (also called “fin”) folded over an inner portion 3 so as to define an inner annular space 4 between and bounded by the outer and inner portions 2 and 3. The inner annular space 4 is in fluid communication with a fluid (e.g., water, not shown) flowing in a pipe sealed by the seal 1. The fluid enters inner annular space 4 via apertures 5 formed in a side wall of seal 1 (seven such apertures 5 are shown in the drawing). The fluid applies pressure in inner annular space 4 to increase tightening of the seal. The apertures 5 have two end faces: one end face is open to the outer side wall of seal 1 and the other end face is open to the inner annular space 4.
The hydraulic seal 1 is constructed in the prior art from a long rubber strip (such as a length of 25 meters). The long strip is cut to the size of the desired circumference and the hydraulic inner space is formed by drilling holes in the rubber. The cut rubber strip is then formed into a ring.
It is known in the prior art to form sealing rings by molding the rubber or other elastomer, such as by injection molding. However, it is not heretofore known to make the seals with the hydraulic inner space 4 by molding, because such an inner space of the prior art does not lend itself to molding, such as injection molding.